Did your filament snap?
You check your filament reel and there’s still plenty of material. Yet nothing is still coming out of the extruder. It could be that your filament snapped, an issue that is more prevalent in Bowden feed printers since the filament is concealed. Old and cheap filaments tend to snap easily, so you better make sure that your filaments are stored appropriately. A too-tight idler tensioner can also put pressure on the filament and cause it to snap.
Just remove the filament from the printer as you normally do. If there is remaining filament inside the tube, you would need to separate the tube from the hotend and extruder. You can then heat the nozzle to pull out the filament.
As for the idler tensioner, you can loosen it and only start adjusting the tightness when you start to print.